Both above are on Task 100%
Bayhas and falconsprint are both 100% right and Dietrich must have missed the possibility of limpmode being a possibility as well. We recently also had an issue with the pickup horn (is dependent on vacuum suction.... even being hit while driving can cause a loss of oil suction, thus reasoning for placement at oil-pan base and crown in fill horn scrren holder, etc. Address visual oil movement first under oil fil cap.... then move to rest of concerns. Have movement... then close it and move on.... no movement, check filter and think about dropping that lower pan and clearing that oil screen and possible sludge under valve covers. There are passages in both valve cover tops (similar to sinuses for the engine compartment and both have drains that need to be clear for oily vapor blowby residue to drain back). If not serviced regular or if sits for any length of time..... an issue can build!
As post stated, dependent on length sitting, that oil can wax up and cause a havoc with galley ways, drains, etc. Many of the passages are very small and at high rpm, bearing surfaces extremely dependent of good lubricant between surface faces. Remember high flow=low pressure.... low flow= higher pressure dependent on oil viscosity, dependent on temperature.... An overheating engine will many times lose it's oil pressure due to thinning of oil and very very high lubricant flow, etc. Vicious Circle my friend!
At engine operating Temperature the 120 and 119 engines require 10 wt for proper overall lubrication needs..... in fact all four cycle engines, even those using a single grade lubricant will have 10 wgt lubricant flowing in their machines at operating temperature. to be sustained.
One of our clients mentioned a site that also has this information. Someone on this site can also help with the actual site information?I picked this up in engineering, etc.
I will get with Dietrich..... please follow the previous Post advice and address the oil pressure anomaly
first and Always First
!!!. You may have fine oil flow and your sender is only seeing data below it's calibrated sensor engineered curve, etc.
After verifying you have actual oil flow through the oil fill cap.... then take a look at those cylinders, regarding the idle. Like Dietrich eluded too, there are a lot of sharp cookies on this site... and all have their advice to offer and you can choose from there! Well, as far as me, I'm not the sharpest tool in the shed, but I sure get used alot........ LOL :surrender:
Although many of the other mechanics use 20-50 and such for their Benz... in my 94' S420 119.971 (347K miles), I utilize 0-30 SAE Mobil-1 and ensure that at start-up.... my lifters, journals, cam bearing towers are bathed in lubricant. There is nothing wrong with 20/50 SAE and many of our Senior Master Mechanics use it in their high mileage vehicles..... I just feel otherwise and if my engine gets a little noisy I will address that lifter or oil tube, etc. At least my start-up worries are satisfied.... always!
Thanks to everyone.... Robert O.
you have 3 separate problems.
rough idle with hissing sound: you have major vaccum leak, follow the sound and you ll find the broken/deattached vaccum line
oil pressure: check oil level and viscosity, mercedes manual does not want you alarmed if the the oil pressure is 0 at idle, as long as the red light is not on, and the needle goes up in pressure as soon as you rev up. do an oil change anyway and see what happens.
if the pressure does not go up when you hit the gas, DO NOT DRIVE THE CAR AND TURN IT OFF RIGHT AWAY
hard to push gas pedal: from what you are describing, the car is in the limp home mode
if the car is idling, and you hit the gas, does the pedal travel 1/2 way to the floor before the rev goes up?